Magnetic compass



0d. M, i933. F. G. scHwEusTx-{AL L? MAGNETIC COMPAS S Filed March 3l, 1930 Patented oct. 17, 1933 1,930,775

MAGNETIC COMPASS Fred G. Schweisthal, Chicago, Ill., assignor to Stewart-Warner Corporation, Chicago, Ill., a corporation of Virginia Application March 31, 1930. Serial No. 440,274

4 Claims. (Cl. 33-223) The purpose of this invention is to provide an cup and the upper surface of the bottom plate, B, improvementinmagnetic Compasses adapted par-` and the aperture through the hollow bolt being ticularly for aerial vehicles. It consists in the closed at the lower end by a screwed-in plug h3.` elements and features of construction shown and Said cup member, G, has toward the bottom, aperdescribed as indicated inthe claims. tures, g1, g1, for communication from the cup 60 In the drawing: cavity to the cavity of the casing outside the cup. Figure 1 is a top plan view of an instrument The purpose of the casing construction as thus far embodying this invention, described is to adapt it to be occupied with liquid Figure 2 is a section at' the line, 22, on for certain purposes hereinafter .set forth, the Figure 1. hollow bolt at the bottom serving upon withdraw- 65 Figure 3 is a detail section upon an enlarged ing the plug, h3, for filling and draining the casing scale of a portion of Figure 2. chamber.

Figure 4 is a partly sectional view showing in For mounting the magnetic needle and comside elevation the pendulous universally pivoted pass card pendulously so that the needle and carrier for the compass for the magnetic needle compass card may maintain horizontal position 70 and compass card, the bottom of the casing bethroughout all changes of inclination of the ing shown in section. vehicle in its aerial travel, there vis provided a Figure 5 is a detail section at the line, 5-5, on suitably long step bearing member, K, constitut- Figure 2. ing a pendulous weight and having at its lower Figure 6 is a detail section showing a modiflcaend a step bearing, 40, for the spindle, L, which 75 tion of the corresponding structure of Figure 2. has near its upper end a second bearing, 41, and

In the drawing the compass represented is which has secured to it at its upper end above shownhaving its casing mounted fixedly upon a said step bearing a fitting, 50, onto which there xed bracket, A, said casing comprising abottom are clamped by bolts, 51, 51, the compass card,

plate, B, and a top annular plate or clamping M, and a magnet-needle-securing member, N, 80 flange, C, bound together by four bolts, F, of the latter having oppositely extending arms, whichone may be seen in Figure 2, clamping be- N1, N1, formed at their extremities for seating tween them a transparent body, D, and at the and holding clamped against the under side of upper .end of said body a transparent face plate, the compass card, M, two parallel magnetic E, with suitable packing gaskets, b, at the opneedles, O, O, shown circular in cross section, 85 posite ends of said transparent body, D, and at constituting Ithe magnet element. The step bearopposite sides of the transparent face plate, E, ing member, K, is carried by securement at its for making the enclosed chamber liquid tight. upper end to an inner gimbal ring, P, which is `For mounting the casing on the bracket the botpivoted by its opposite gudgeons, p, p, at diatom plate, B, has three short foot bosses, 20, 20, metrically opposite points in an outer gimbal 90 20, by which the casing is secured to the horiring, R, which in turn is pivoted by its gudgeons, zontal flange, A1,of the bracket by means of bolts, r, at opposite ends of a diameter in a vertical 2l, insulating and cushioning washers, 22 and 23, plane at right angles to the plane of the being interposed at opposite sides of the web, A1, gudgeons, p, p, in upwardly projecting lugs, G1,

between said web, and the head of the bolt and G1, of the support, G, said lugs projecting above 95 the bottom of the foot bosses, 20, respectively, the remainder of the upper edge of the cup so suitable metal washer, 24, being interposed beas to position the said gimbal ring, R, high tween the head of the bolt and the insulatingenough to permit it to clear the upper edge of washer, 22. the cup member, G, in the tilting movement Within the casing there is mounted rigidly upon which it may derive in the changing level of 100 the bottom plate,B, an upwardly open cup-shaped the vehicle and the fixed supporting bracket, A. supporting member, G, for supporting pendulously The detail construction indicated is designed as hereinafter described, the magnetic needle and to facilitate assembling of the parts as follows: compass card, said member, G, being secured to The jewel, 41, is placed over the upper end of the the plate, B, by means of a hollow bolt, H, havspindle, L, and the bushing, 50, is then pressed 105 ing its head, h, stopped upon the upper side of the onto the spindle to its required position. Strap, bottom of the cup member anda gasket, h1, inter- N, is placed in position on the bushing, 50; the posed at the under side of the bottom between the magnets, O, O, are placed in the seating cavities same and a clamping nut, h2, an extended gasket, of the strap, N, and the compass card, M, is ap- J, being interposed between the bottom of the plied Over the' magnet mount or strap, N, with the ll0 raf" Washer, 50', above it on the bushing, 50, and to complete the assembly they are securely clamped by screws, 51.

The inner gimbal ring, P, is adapted to be assembled pivotally in the outer gimbal ring, R, by the provision of flanged bearing bushings, 42, 42, fitted to suitable apertures in the outer ring, R, as seen in Figure 3, the inner gimbal ring being introduced into the outer gimbal ring with its pivots, p, in alignment with the apertures in the outer ring, and the bushing bearings being then inserted from the outer side of the outer ring, and retaining springs, 45, 45, are secured at their lower ends to the outer side of the ring, R, and at their upper ends formed forl engaging the outer ends of the bushings as seen in Figure 3. This construction permits ready assembling and disassembling of the parts, the retaining springs, 45, being adapted to swing sidewaysfa sufficient distance for admitting and withdrawing the bushings as described.

The outer gimbal ring is similarly arranged for assembling in the support, G, by means of bearing bushings, 52, 52, retained in place by springs, 55, 55, secured to the outer side of the support, G.

The compass card, M, has direction readings upon its upper face exposed for reading through the transparent face plate, E, of the instrument. The index member cooperating with the compass card for reading the indication of the compass is afforded by a rod or bar, S, mounted iixedly on the upper gimbal ring, and thereby on the step bearing member, K, and extending diametrically across under the compass card and up-turned at the ends outside the circumference of the compass card so as to have at each upper end an outwardly turned index terminal, s, which is positioned substantially in the plane of the compass card and exposed immediately outside the circumference of the latter so that its registration with the direction readings of the compass card may be accurately noted without mistake due to parallax. This index member, S, it will be understood, is mounted fixedly, as stated, with respect to the step bearing member in which the needle and compass card are pivoted, as is necessary in order that the reading of the compass card by reference to the index terminal of said rod shall indicate correctly the direction in which the vehicle is headed for movement of travel,-in the direction of the longitudinal dimension or direct fore-and-aft line of the vehicle which is commonly indicated by a mark on the compass box called the lubber line. And accordingly this index member, S, may be hereinafter referred to as the lubber line rod.

As mentioned above, the casing isgadapted and designed to be filled with liquid for the purpose of damping the oscillation of the needle and compass card; and for amplifying the damping effect, the compass card is formed with a downwardly projecting peripheral flange M1, which has on its outer surface direction readings corresponding to those on the face of the compass card. And it will be noticed that the lubber line indicator in its extent from its mounting at the step bearing member, K, to the point where it is folded upwardly, necessarily extends under the lower edge of the flange, M1, so that its upward extent for reaching the plane of the compass card at which it carries the index terminal, s, stands closely adjacent to the outer face of the flange, M1, and at that part serves as an index co-operating with the direction readings of the flange for reading the direction indication afforded by the compass, such reading being rendered possible by the transparent enclosing wall, D.

To provide for expansion and contraction of the liquid with which the chamber is filled for cooperating with the compass card to damp the oscillation of the card and the magnetic element, O, O, the bottom plate, B, has at one side of the position of the member, G, a slight annular boss, b1, encompassing an air vent aperture, b2, and there is clamped onto this boss a flexible dlaphragm, b4, interposed between impervious gaskets, b5 and be, respectively, above and below the diaphragm; the clamping ring, b3, is split or l slotted at Z230, and the upper gasket, b5, is similarly split to release any air which might otherwise be trapped over the diaphragm, b4. The aperture, b2, admits atmospheric pressure to the chamber below the diaphragm, and the liquid fills4 the chamber above the diaphragm. The diaphragm is flexibly resilient and adapted to extend substantially without deflection from the plane ln which it is mounted by the weight of the liquid in the chamber as the latter is normally f'llled. Upon expansion of the liquid due to rise in temperature,

the diaphragm yields into the lower chamberwhich is accordingly dimensioned for taking care of the expansion of the liquid due to the maximum anticipated rise of temperature above ythat at which the chamber was filled. And upon the lowering of the temperature, causing shrinkage of the liquid, atmospheric pressure on the diaphragm, causes it to be deected into the upper chamber, absorbing the shrinkage and preventing the creation of empty space in the easing. Figure 6 illustrates the substitution of a small bellows of the sylphon type in place of the diaphragm for response to expansion or contraction of the liquid.

1. A magnetic compass comprising a fixed mount and a magnet element carrier pendulously universally pivoted on said fixed mount; a magnet element having a spindle carried by the carrier; a compass card fixed for rotation with the magnet element, and a lubber line indicator mounted fixedly on the carrier for movement therewith in the pendulous swinging oscillation of the latter, the fixed mount comprising a sealed chamber filled with liquid; the carrier being universally pivoted pendulously within said chamber; whereby the compass card co-operates with the liquid for damping the oscillation of the magnet element.

2. A magnetic compass comprising a fixed mount and a magnet element carrier pendulously universally pivoted on said fixed mount; a magnet element having a spindle carried by the carrier; a compass card fixed for rotation with the magnet element, and a lubber line indicator mounted fixedly on the carrier for movement therewith in the pendulous swinging oscillation of the latter, the fixedmount comprising a sealed chamber filled with liquid; the carrier being universally pivoted pendulously within said chamber; the compass card having a flange projecting transversely of the plane of said card at the side opposite the compass readings for affording increased surface for liquid contact for damping the oscillation and 3. A magnetic compass comprising a fixed mount and a magnet element carrier pendulously universally pivoted on said fixed mount; a magnet element having a spindle carried by the carrier; a compass card xed for rotation with the magnet element, and a lubber line indicator mounted xedly on the carrier for movement therewith in the pendulous swinging oscillation of the latter, the compass card having -a flange projecting transversely of the plane of the card at the side opposite the face having the compass readings, the lubber line indicator being carried by securement to the spindle bearing and extended out under and outwardly past said flange and upwardly immediately adjacent the ange to the plane of the card, the xed mount comprising a transparent enclosing wall encompassing the pendulous universally pivoted carrier and all parts carried thereby, the compass card ange having direction readings on its outer surface, whereby the compass indication may be read both from the side and the face of the instrument.

4. In a magnetic compass having a magnet element and a spindle on which it is mounted, said magnet element comprising a pair of magnets and a compass card; a clamping bar for holding the magnets to the compass card in position parallel to each other, the compass card having a central aperture, and the clamp having an aperture adapted to register with the compass card aperture when holding the magnets in their said parallel positions; a anged bushing; a washer fitted to the bushing, and bolts for clamping the clamping bar to the compass card between the washer and the ange of the bushing, the bushing being centrally apertured for forced t on the spindle.

FRED G. SCHWEISTHAL. 

